This invention is directed to a high current density ion source, and particularly to an arrangement for focusing the ions extracted from the discharge in an electron bombardment ion source.
Electron bombardment ion sources are known for the production and acceleration of ion beams. Kaufman U.S. Pat. No. 3,156,090 is the original application of electron bombardment ion sources to space thrusters. Petrick U.S. Pat. No. 3,159,967 is another disclosure of that kind of source. Speiser et al. U.S. Pat. No. 3,311,772 discusses the problem of providing uniform thrust direction for an electron bombardment ion thruster in which the plasma density is nonuniform across the source. Prior effort has been directed to the problem of providing an ion beam which has a uniform thrust direction for maximum thrust efficiency.